As a cutting tool with detachable insert used for grooving or cutting-off of a work material, there is a tool having the following structure. In this tool, a pair of jaw portions is formed in an elastic deformable manner at the tip of a holder. A pressing surface is provided in one jaw portion of the pair of jaw portions. A pedestal surface is provided in the other jaw portion of the pair of jaw portions. The pressing surface and the pedestal surface are arranged so as to face each other. An insert attachment seat which clamps and attaches a cutting insert having cutting blades are formed by the pressing surface and the pedestal surface. In Patent Document 1, a cutting tool with detachable insert in which this insert attachment seat is formed in a head member detachably mounted on the tip portion of the holder is suggested.    [Patent Document 1] Japanese Patent Unexamined Publication No. 05-192802